1. Field of the Invention
This invention is directed toward a washing system for washing turbines on-line. The invention is also directed toward a method for washing turbines on-line.
2. Description of the Related Art
Turbines lose their efficiency when the turbine blades become dirty during use and production is lost. The aerodynamic efficiency of the blades is reduced as a dirt film forms on the blades. It is known to wash the blades to remove the film to maintain their efficiency. The washing usually occurs when the turbine is off-line. The turbine is filled with washing liquid, including detergents, when off-line and is rotated at ‘crank’ speed. The turbine is rotated long enough to allow the turbine blades a good long soak in the washing liquid thus allowing better cleaning. Production is of course lost while the turbine is off-line.
It is known to clean turbines on-line by spraying washing liquid onto the blades to maintain efficiency at peak levels. On-line cleaning is more cost efficient than off-line cleaning since there is no down-time for the turbine. However, the washing liquid normally employs a detergent or cleaning compound to remove the dirt, and the detergent or cleaning compound could present an environmental problem. The detergent or cleaning compound used in the washing liquid could also leave a film or coating on the blades after cleaning thereby affecting turbine efficiency. Therefore on-line turbine cleaning with a detergent usually still needs to be supplemented with the off-line cleaning, but not as frequently as when only off-line cleaning is used.
The water usually employed in the washing liquid in turbine cleaning is not very clean. The water normally has minerals in it which could foul the blades being cleaned. The water normally used can also have some suspended solids and/or other impurities therein which can lead to a fine coating or film being left on the blades being cleaned and which also could damage the surface of the blades.
Clean water can be produced for use in turbine cleaning by reverse osmosis or by desalinization systems. It has been found that spraying clean water only, without detergent or cleaning compounds, on the turbine blades, while the turbine is on-line, can help clean the blades and thus extend the time between off-line cleanings. However the water obtained by reverse osmosis is relatively expensive since the filtering membrane used in the reverse osmosis systems must be frequently changed. Desalinization systems also produce relatively expensive water. The water obtained from both systems also is still not clean enough to effectively and efficiently clean the turbines. Water produced by the reverse osmosis process, for example has a conductivity of about 4 microsiemens/cm and a total dissolved solids (TDS) count of about 3 ppm or more and this amount of solids and impurities in the water could cause some damage to the blades being cleaned and can also still leave a fine film coating on the blades affecting their efficiency.
Turbines are often used in remote locations, away from water distribution networks, where it is difficult to provide a sufficient supply of clean, inexpensive, cleaning water. Turbines are used to provide power, for example, in gas or oil fields in hot, arid regions that are water poor. Providing any source of water to clean the turbines in these locations can be very costly. Relatively clean water can be provided by desalinization, if the turbines are located close to salt water or by transporting water in to the turbines from locations where water is more abundant, the water being treated by reverse osmosis before or after transport. However, these methods of providing water are obviously very costly and also, as noted above, do not provide very clean water for use in on-line turbine cleaning.